snRNA genes are an unusual class of genes transcribed by RNA polymerase II. Transcription of these genes does not require a TATA box but rather is directed by a sequence at about -60, the PSE. We are studying the sea urchin system as a model system for snRNA biosynthesis. During early embryogenesis in the sea urchin, there is a rapid synthesis of snRNA genes between the morula and blastula stage. The snRNA genes expressed in early development are encoded in tandemly repeated units. Between the blastula and the gastrula stage these tandemly repeated genes are inactivated and the rate of snRNA synthesis drops. In the larva stage and in somatic cells the snRNAs are expressed from a second set of genes which are present in low copy number. The low copy genes are expressed constitutively during embryogenesis. Using microinjection of genes into sea urchin zygotes, the promoter elements necessary for proper temporal expression of these genes will be mapped. The factors involved in controlling expression of the genes will be isolated using DNA affinity chromatography and a functional assay based on in vitro transcription of the genes. The control of expression of these factors during early embryogenesis will be studied. The biochemical mechanism of snRNA 3' end formation will be studied both in sea urchins and mammalian cells.